Providing unit of work continuity in the event initiating client fails over

ABSTRACT

A method is provided for providing unit of work continuity between a client device and a server when the client device initially fails to complete an ongoing unit of work. The method includes temporarily storing, in a temporary storage location in the server, in-doubt messages sent to the server for the ongoing unit of work, when the client device disconnects from the server without committing the ongoing unit of work so that the client device does not have to resend the in-doubt messages to the server. The method further includes utilizing unique hash-codes to identify the in-doubt messages the client device had earlier sent so that the server can retrieve the in-doubt messages from the temporary storage location and include the in-doubt messages as part of the ongoing unit of work to be committed by the client device. The ongoing unit of work is only part of an entire transaction.

BACKGROUND Technical Field

The present invention relates generally to information processing and,in particular, to providing unit of work continuity in the event theinitiating client fails over.

Description of the Related Art

Transactions play a very important role within the enterprise system toprovide data integrity. Transactions provide an “all-or-nothing”proposition, stating that each unit of work performed in a resourcemanager (messaging or database) must either complete in its entirety orhave no effect whatsoever. A transaction can be considered as acollection of two or more units of work

One of the key aspects of transactions is to recover from failures. Mostof the existing solutions to recover transactions revolve around servercrashing and restarting. There is no solution to deal with transactionrecovery or continuity of the in-doubt transactions when the client thatstarted the transaction fails and restarts. Currently, when the clientcrashes in between the transaction (i.e., the client fails withoutissuing the commit), the only solution is for the resource managers tojust roll back all the messages.

Presume we have a messaging application that sends several (100messages) messages, each of 1 MB size within a single group. As per thetransaction policy until the client issues the commit, theresource/transaction manager will not make the messages available forconsumption. Presume after the client sent 95 messages, the clientcrashes. Since the client crashed, the resource manager just rolls backall the 95 messages.

Currently, when the client application fails over and reconnects, theclient has to again resend all the messages from starting. This causes asignificant congestion of the network creating performance, latency andnetwork band-width issues.

All of the prior art only addresses server side recovery of messageswhen the server crashes and restarts. None of the prior art addressproviding continuity at a unit of work level in the event the clientcrashes and reconnects.

SUMMARY

According to an aspect of the present principles, a method is providedthat, in turn, provides unit of work continuity between a client deviceand a server when the client device initially fails to complete anongoing unit of work. The method includes temporarily storing, in atemporary storage location in the server, in-doubt messages sent to theserver for the ongoing unit of work, when the client device disconnectsfrom the server without committing the ongoing unit of work so that theclient device does not have to resend the in-doubt messages to theserver. The method further includes utilizing unique hash-codes toidentify the in-doubt messages the client device had earlier sent sothat the server can retrieve the in-doubt messages from the temporarystorage location and include the in-doubt messages as part of theongoing unit of work to be committed by the client device. The ongoingunit of work is only part of an entire transaction.

According to another aspect of the present principles, a computerprogram product is provided that, in turn, provides unit of workcontinuity between a client device and a server when the client deviceinitially fails to complete an ongoing unit of work. The computerprogram product includes a computer readable storage medium havingprogram instructions embodied therewith. The program instructions areexecutable by a computer to cause the computer to perform a method. Themethod includes temporarily storing, in a temporary storage location inthe server, in-doubt messages sent to the server for the ongoing unit ofwork, when the client device disconnects from the server withoutcommitting the ongoing unit of work so that the client device does nothave to resend the in-doubt messages to the server. The method furtherincludes utilizing unique hash-codes to identify the in-doubt messagesthe client device had earlier sent so that the server can retrieve thein-doubt messages from the temporary storage location and include thein-doubt messages as part of the ongoing unit of work to be committed bythe client device. The ongoing unit of work is only part of an entiretransaction.

According to yet another aspect of the present principles, a system isprovided. The system includes a server configured to temporarily store,in a temporary storage location in the server, in-doubt messages sent tothe server for an ongoing unit of work, when a client device disconnectsfrom the server without committing the ongoing unit of work so that theclient device does not have to resend the in-doubt messages to theserver. The server is further configured to utilize unique hash-codes toidentify the in-doubt messages the client device had earlier sent sothat the server can retrieve the in-doubt messages from the temporarystorage location and include the in-doubt messages as part of theongoing unit of work to be committed by the client device. The ongoingunit of work is only part of an entire transaction.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 shows an exemplary processing system to which the presentprinciples may be applied, in accordance with an embodiment of thepresent principles;

FIG. 2 shows an exemplary system for providing unit of work continuityin the event the initiating client fails over, in accordance with anembodiment of the present principles;

FIG. 3 shows an exemplary method for server/Resource Manager storage ofin-doubt messages, in accordance with an embodiment of the presentprinciples;

FIGS. 4-5 show an exemplary method for client unit of work continuityand server retrieving stored messages, in accordance with an embodimentof the present principles;

FIG. 6 shows an exemplary cloud computing environment, in accordancewith an embodiment of the present principles; and

FIG. 7 shows an exemplary set of functional abstraction layers providedby the cloud computing environment shown in FIG. 6, in accordance withan embodiment of the present principles.

DETAILED DESCRIPTION

The present principles are directed to providing unit of work continuityin the event the initiating client fails over.

As used herein, the term “unit of work” refers to one or more actionsand/or occurrences relating to a transaction, but not all of the actionsrelating to that transaction. That is, a unit of work is limited to asubset of the actions required to be performed or to occur in atransaction.

As an example, consider the following. In the example, a transaction isdefined as involving the transmission of 100 messages. A unit of workfor that transaction can span one or more subsets of the entire 100messages. In further detail for this example, a first unit of work caninvolve sending the first 50 messages, while a second unit of work caninvolve sending 49 messages, while a third and final unit of work forthat transaction can involving sending the 1 final message, for a totalof 100 messages involves across all of the preceding units of work.

In the case where a unit of work is suspected of being in-doubt, thepresent principles provide a solution that avoids having to resend thein-doubt messages from the client to the server due to the serverdiscarding the same. In such a case, the present principlesadvantageously provide a way for the server to identify that it hasreceived these in-doubt messages and to retrieve these messages from atemporary storage of the server, thus saving all of the resourcesinvolved in retransmission of these messages. As is readily appreciatedby one of ordinary skill in the art, the present principles can beapplied to the above and numerous other scenarios, as readily envisionedby one of ordinary skill in the art given the teachings of the presentprinciples provided herein, while maintaining the spirit of the presentprinciples.

As used herein, the term “in-doubt message” refers to a message forwhich a commit or rollback instruction for the overall transaction thatincludes the unit of work that, in turn, includes the message, has yetto be received from the client. That is, as used herein, the term“in-doubt messages” refer to messages in a unit of work that have beenprepared but a decision (commit/rollback) has yet to be conveyed fromthe client to the server.

Thus, the present principles are advantageously directed to the conceptof “unit of work efficiency and continuity” for client fail overs, wherethe present principles efficiently attempt to continue the unit of workbefore discarding the messages. As used herein, the term “fail over” andsimilar terms refer to the case where a client has disconnected from theserver before a decision (commit or rollback) has been received for anoverall transaction.

FIG. 1 shows an exemplary processing system 100 to which the presentprinciples may be applied, in accordance with an embodiment of thepresent principles. The processing system 100 includes at least oneprocessor (CPU) 104 operatively coupled to other components via a systembus 102. A cache 106, a Read Only Memory (ROM) 108, a Random AccessMemory (RAM) 110, an input/output (I/O) adapter 120, a sound adapter130, a network adapter 140, a user interface adapter 150, and a displayadapter 160, are operatively coupled to the system bus 102.

A first storage device 122 and a second storage device 124 areoperatively coupled to system bus 102 by the I/O adapter 120. Thestorage devices 122 and 124 can be any of a disk storage device (e.g., amagnetic or optical disk storage device), a solid state magnetic device,and so forth. The storage devices 122 and 124 can be the same type ofstorage device or different types of storage devices.

A speaker 132 is operatively coupled to system bus 102 by the soundadapter 130. A transceiver 142 is operatively coupled to system bus 102by network adapter 140. A display device 162 is operatively coupled tosystem bus 102 by display adapter 160.

A first user input device 152, a second user input device 154, and athird user input device 156 are operatively coupled to system bus 102 byuser interface adapter 150. The user input devices 152, 154, and 156 canbe any of a keyboard, a mouse, a keypad, an image capture device, amotion sensing device, a microphone, a device incorporating thefunctionality of at least two of the preceding devices, and so forth. Ofcourse, other types of input devices can also be used, while maintainingthe spirit of the present principles. The user input devices 152, 154,and 156 can be the same type of user input device or different types ofuser input devices. The user input devices 152, 154, and 156 are used toinput and output information to and from system 100.

Of course, the processing system 100 may also include other elements(not shown), as readily contemplated by one of skill in the art, as wellas omit certain elements. For example, various other input devicesand/or output devices can be included in processing system 100,depending upon the particular implementation of the same, as readilyunderstood by one of ordinary skill in the art. For example, varioustypes of wireless and/or wired input and/or output devices can be used.Moreover, additional processors, controllers, memories, and so forth, invarious configurations can also be utilized as readily appreciated byone of ordinary skill in the art. These and other variations of theprocessing system 100 are readily contemplated by one of ordinary skillin the art given the teachings of the present principles providedherein.

Moreover, it is to be appreciated that system 200 described below withrespect to FIG. 2 is a system for implementing respective embodiments ofthe present principles. Part or all of processing system 100 may beimplemented in one or more of the elements of system 200.

Further, it is to be appreciated that processing system 100 may performat least part of the method described herein including, for example, atleast part of method 300 of FIG. 3 and/or at least part of method 400 ofFIGS. 4-5. Similarly, part or all of system 200 may be used to performat least part of method 300 of FIG. 3 and/or at least part of method 400of FIGS. 4-5.

FIG. 2 shows an exemplary system 200 for providing unit of workcontinuity in the event the initiating client fails over, in accordancewith an embodiment of the present principles.

The system includes one or more client computing devices (collectivelydenoted by the figure reference numeral 210) and a server (hereinafterinterchangeably referred to as a “resource manager” (RM)) 220. In theembodiment of FIG. 2, three client computing devices are shown, namelyclient computing devices 210A, 210B, 210C, and 210D. However, for thesake of illustration, the following description and examples will focuson client computing device 210A (hereinafter referred to as “client”210A in short) as being a failed over client that(unintentionally/undesirably) disconnects from the server 220. As such,for the purposes of the present principles, the client 210A can also bereferred to as a “failed-over client” at the times when the client 210Ahas suffered as fail-over. In an embodiment, system 200 can beimplemented using a cloud configuration (see, e.g., FIGS. 6-7).

Further regarding client computing devices 210, the same can involve anytype of client computing device. In the embodiment of FIG. 2, the clientcomputing devices 210 include a server 210A, a smartphone 210B, adesktop computer 210C, and a laptop 210D, for the sake of illustration.Of course, other client computing devices can be used. Moreover, inother embodiments, the client computing devices 210 can be of the sametype or include at least two of the same type. These and othervariations of client computing devices to which the present principlescan be applied are readily determined by one of ordinary skill in theart, while maintaining the spirit of the present principles.

The server/resource manager 220 of system 200 differs a transactionmanager as known and used in the prior art in that the server/resourcemanager 220 is able to store and process units of work that in all caseswill be less than all of the work required for a transaction. This levelof granularity provides many advantages over that provided by aconventional transaction manager, as readily appreciated by one ofordinary skill in the art.

The client 210A and the server 220 are configured to exchangeinformation there between. In an embodiment, the information can bemessages. However, any type of information can beinvolved/exchanged/communicated, while maintaining the spirit of thepresent principles. For example, the present principles can also be usedfor databases. As a further example, the present principles can be usedfor database updates, in databases or database systems where the samecan maintain an intermediate state.

The exchange of information can occur over one or more networks(collectively denoted by the figure reference numeral 288). The one ormore networks 288 can include any type of networks such as, for example,but not limited to, cellular networks, local area networks, wide areanetworks, personal area networks, wireless networks, wired networks, anycombination of the preceding, and so forth. In the embodiment of FIG. 2,the one or more networks 288 are implemented by one or more wirelessnetworks for the sake of illustration.

In an embodiment, the present principles are configured to provide asolution for the server 220 to temporarily store the in-doubt messageswithout discarding them when the client 210A disconnects withoutcommitting the ongoing unit of work.

In an embodiment, the server 220 is configured to identify thefailed-over client 210A that had earlier sent the messages, so that theclient 210A does not have to resend all the messages again.

In an embodiment, the present principles are configured to provide amechanism for the server 220 to send a list of unique hash-codes for thein-doubt message that the server 220 is temporarily storing to thefailed over client 210. Each in-doubt message will have its own uniquehash-code in order to uniquely identify the specific in-doubt messagecorresponding to that unique hash code.

In an embodiment, the present principles are configured to allow thefailed-over client 210 to check for matching hash-codes in the list sentby the server 220. If a particular hash code is present, then the client210A just sends back the hash code from the list (that identifies arespective in-doubt message temporally stored by the server 220) insteadof the physical message to the server 220. In this way, bandwidth,processing, and other resources are saved while also reducing latency(e.g., involved in a retransmission). Thus, retransmission costs arebeneficially avoided by the present principles.

In an embodiment, the present principles are configured to have theserver 220 retrieve the message from its temporary stored location andmake the message part of the ongoing unit of work to be committed by theclient 210A.

Regarding identifying a client as a failed client, in an embodiment, anymechanism can be used to keep an in-flight business object when a unitof work is tagged as “failed”. We can, for example, use the identity ofthe client, similar to the durable subscription clientID principle. Incase of a durable subscription, the client always sets its desiredclientID, either reading it from the ConnectionFactory, or eXtensibleMarkup Language (XML) or some other way that only the client knows. Eachof the clients essentially set this clientID without serverinterference. Of course, other mechanisms and approaches can also beused in accordance with the teachings of the present principles, whilemaintaining the spirit of the present principles. For example, a mediaaccess control (MAC) address, unique business data (e.g., a phonenumber, a unique customer number, a unique business transactionidentifier, and so forth), and so forth.

FIG. 3 shows an exemplary method 300 for server/Resource Manager storageof in-doubt messages, in accordance with an embodiment of the presentprinciples. The method 300 involves a server (e.g., server 220) and afailed over client (e.g., client 210A).

At step 305, connect, to the server by the client, using a specificunique identifier (hereinafter “unique id) that indicates that theserver must store in-doubt messages for a specific unit of work. In anembodiment, the unique id can be any type of identifier, as long as itcan function to identify 2 different clients uniquely and also ensurewhen a failed-over client reconnects that client can use the same uniqueid.

At step 310, calculate, by the client, for each message generated by theclient, a unique attribute for this message, and send the uniqueattribute and the message corresponding thereto to the server. Theunique attribute could be a hash-code, a custom algorithm to identifythe uniqueness of the message, and/or so forth. The unique attribute andthe message corresponding thereto (that is, from which, or for which, itwas calculated) can be sent in-band (together) or out-of-band(separately), but in both cases associated with each other (the messageand its unique attribute). For the sake of illustration, the uniqueattribute is interchangeably referred to as a hash code.

At step 315, store, by the server, both the unique attribute and themessage (pay load).

At step 320, store, by the server, the messages sent within a unit ofwork, responsive to the client abruptly disconnecting from the serverwithout issuing a commit/rollback the server.

At step 325, retain, by the server, the messages sent within the unit ofwork until a pre-configured timeout expires.

At step 330, discard, by the server, the in-doubt messages, responsiveto the client not reconnecting to the server within the time period ofthe pre-configured timeout. Thus, as used herein, the term “in-doubtmessages” refer to messages in a unit of work that have been preparedbut a decision (commit/rollback) has yet to be conveyed to the server.

FIGS. 4-5 show an exemplary method 400 for client unit of workcontinuity and server retrieving stored messages, in accordance with anembodiment of the present principles. The method 400 involves a server(e.g., server 220) and a failed over client (e.g., client 210A).

At step 405, provide, by the same client, the same unique id to theserver, responsive to the same client reconnecting or the failed-overinstance of the client reconnecting.

At step 410, check, by the server, in its (the server's) repositorywhether or not there are any in-doubt messages for the client having thesame client unique id (that is, the client of step 405).

At step 415, send, by the server, back to the client, a list of all thehash codes that it has stored.

At step 420, generate, by the client, a message.

At step 425, check, by the client before sending the message generatedat step 440, the client libraries to determine whether or not the hashcode received from the server matches with (the hash code for) anymessage sent to the server. If so, then continue to step 430. Otherwise,continue to step 445.

At step 430, send, by the client (e.g., using client libraries), thehash-code or the sequence number to the server (instead of the clientsending the physical message to the server), indicating the message mustbe retrieved from its temporary storage. Step 430 is performedresponsive to the hash code (or other unique attribute) matching anymessage sent by the server (as determined at step 425).

At step 435, retrieve, by the server, the message and puts the messagewithin the ongoing unit of work as though the client had sent themessage.

At step 440, send, by the server, an acknowledgement back to the clientindicating the message was successfully retrieved. This is an indicationto the client that the message is now available at the server.

At step 445, send, by the client, the complete message to the server.This new message is accepted by the server and a similar acknowledgementis sent back to the client. Step 445 is performed responsive to the hashcode (or other unique attribute) not matching any message sent by theserver (as determined at step 425) such that the client wants to send anew message.

At step 450, receive, by the server from the client, a commit.

At step 455, check, by the server, whether or not there are any morein-doubt messages in its list, responsive to the client (completing thesending of all the messages and) issuing the commit. This could happenif the client generated any new message or did not use the old message.If so, then continue to step 460. Otherwise, terminate the method.

At step 460, discard, by the server, the in-doubt messages temporarilystored by the server. Step 460 is performed in consideration of the factthat the client has issued a commit (received by the server at step450).

It is to be understood that although this disclosure includes a detaileddescription on cloud computing, implementation of the teachings recitedherein are not limited to a cloud computing environment. Rather,embodiments of the present invention are capable of being implemented inconjunction with any other type of computing environment now known orlater developed.

Cloud computing is a model of service delivery for enabling convenient,on-demand network access to a shared pool of configurable computingresources (e.g., networks, network bandwidth, servers, processing,memory, storage, applications, virtual machines, and services) that canbe rapidly provisioned and released with minimal management effort orinteraction with a provider of the service. This cloud model may includeat least five characteristics, at least three service models, and atleast four deployment models.

Characteristics are as Follows:

On-demand self-service: a cloud consumer can unilaterally provisioncomputing capabilities, such as server time and network storage, asneeded automatically without requiring human interaction with theservice's provider.

Broad network access: capabilities are available over a network andaccessed through standard mechanisms that promote use by heterogeneousthin or thick client platforms (e.g., mobile phones, laptops, and PDAs).

Resource pooling: the provider's computing resources are pooled to servemultiple consumers using a multi-tenant model, with different physicaland virtual resources dynamically assigned and reassigned according todemand. There is a sense of location independence in that the consumergenerally has no control or knowledge over the exact location of theprovided resources but may be able to specify location at a higher levelof abstraction (e.g., country, state, or datacenter).

Rapid elasticity: capabilities can be rapidly and elasticallyprovisioned, in some cases automatically, to quickly scale out andrapidly released to quickly scale in. To the consumer, the capabilitiesavailable for provisioning often appear to be unlimited and can bepurchased in any quantity at any time.

Measured service: cloud systems automatically control and optimizeresource use by leveraging a metering capability at some level ofabstraction appropriate to the type of service (e.g., storage,processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported, providing transparency for both theprovider and consumer of the utilized service.

Service Models are as Follows:

Software as a Service (SaaS): the capability provided to the consumer isto use the provider's applications running on a cloud infrastructure.The applications are accessible from various client devices through athin client interface such as a web browser (e.g., web-based e-mail).The consumer does not manage or control the underlying cloudinfrastructure including network, servers, operating systems, storage,or even individual application capabilities, with the possible exceptionof limited user-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer isto deploy onto the cloud infrastructure consumer-created or acquiredapplications created using programming languages and tools supported bythe provider. The consumer does not manage or control the underlyingcloud infrastructure including networks, servers, operating systems, orstorage, but has control over the deployed applications and possiblyapplication hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to theconsumer is to provision processing, storage, networks, and otherfundamental computing resources where the consumer is able to deploy andrun arbitrary software, which can include operating systems andapplications. The consumer does not manage or control the underlyingcloud infrastructure but has control over operating systems, storage,deployed applications, and possibly limited control of select networkingcomponents (e.g., host firewalls).

Deployment Models are as Follows:

Private cloud: the cloud infrastructure is operated solely for anorganization. It may be managed by the organization or a third party andmay exist on-premises or off-premises.

Community cloud: the cloud infrastructure is shared by severalorganizations and supports a specific community that has shared concerns(e.g., mission, security requirements, policy, and complianceconsiderations). It may be managed by the organizations or a third partyand may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the generalpublic or a large industry group and is owned by an organization sellingcloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or moreclouds (private, community, or public) that remain unique entities butare bound together by standardized or proprietary technology thatenables data and application portability (e.g., cloud bursting forload-balancing between clouds).

A cloud computing environment is service oriented with a focus onstatelessness, low coupling, modularity, and semantic interoperability.At the heart of cloud computing is an infrastructure that includes anetwork of interconnected nodes.

Referring now to FIG. 6, illustrative cloud computing environment 650 isdepicted. As shown, cloud computing environment 650 includes one or morecloud computing nodes 610 with which local computing devices used bycloud consumers, such as, for example, personal digital assistant (PDA)or cellular telephone 654A, desktop computer 654B, laptop computer 654C,and/or automobile computer system 654N may communicate. Nodes 610 maycommunicate with one another. They may be grouped (not shown) physicallyor virtually, in one or more networks, such as Private, Community,Public, or Hybrid clouds as described hereinabove, or a combinationthereof. This allows cloud computing environment 650 to offerinfrastructure, platforms and/or software as services for which a cloudconsumer does not need to maintain resources on a local computingdevice. It is understood that the types of computing devices 654A-Nshown in FIG. 6 are intended to be illustrative only and that computingnodes 610 and cloud computing environment 650 can communicate with anytype of computerized device over any type of network and/or networkaddressable connection (e.g., using a web browser).

Referring now to FIG. 7, a set of functional abstraction layers providedby cloud computing environment 650 (FIG. 6) is shown. It should beunderstood in advance that the components, layers, and functions shownin FIG. 7 are intended to be illustrative only and embodiments of theinvention are not limited thereto. As depicted, the following layers andcorresponding functions are provided:

Hardware and software layer 760 includes hardware and softwarecomponents. Examples of hardware components include: mainframes 761;RISC (Reduced Instruction Set Computer) architecture based servers 762;servers 763; blade servers 764; storage devices 765; and networks andnetworking components 766. In some embodiments, software componentsinclude network application server software 767 and database software768.

Virtualization layer 770 provides an abstraction layer from which thefollowing examples of virtual entities may be provided: virtual servers771; virtual storage 772; virtual networks 773, including virtualprivate networks; virtual applications and operating systems 774; andvirtual clients 775.

In one example, management layer 780 may provide the functions describedbelow. Resource provisioning 781 provides dynamic procurement ofcomputing resources and other resources that are utilized to performtasks within the cloud computing environment. Metering and Pricing 782provide cost tracking as resources are utilized within the cloudcomputing environment, and billing or invoicing for consumption of theseresources. In one example, these resources may include applicationsoftware licenses. Security provides identity verification for cloudconsumers and tasks, as well as protection for data and other resources.User portal 783 provides access to the cloud computing environment forconsumers and system administrators. Service level management 784provides cloud computing resource allocation and management such thatrequired service levels are met. Service Level Agreement (SLA) planningand fulfillment 785 provide pre-arrangement for, and procurement of,cloud computing resources for which a future requirement is anticipatedin accordance with an SLA.

Workloads layer 790 provides examples of functionality for which thecloud computing environment may be utilized. Examples of workloads andfunctions which may be provided from this layer include: mapping andnavigation 791; software development and lifecycle management 792;virtual classroom education delivery 793; data analytics processing 794;transaction processing 795; and unit of work continuity in event ofinitiating client fail over 796.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Having described preferred embodiments of a system and method (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims:

The invention claimed is:
 1. A method of providing unit of workcontinuity between a client device and a server when the client deviceinitially fails to complete an ongoing unit of work, comprising:temporarily storing, in a temporary storage location in the server,in-doubt messages sent to the server for the ongoing unit of work, whenthe client device disconnects from the server without committing theongoing unit of work and in place of the client device resending thein-doubt messages to the server; receiving, by the server from theclient device, a respective one of unique hash codes, calculated by theclient device, for each of the in-doubt messages; and utilizing theunique hash-codes to identify the in-doubt messages the client devicehad earlier sent to retrieve the in-doubt messages by the server fromthe temporary storage location and include the in-doubt messages as partof the ongoing unit of work to be committed by the client device,wherein the ongoing unit of work is only part of an entire transaction.2. The method of claim 1, further comprising sending, by the server tothe client device, a list of the unique hash-codes for the in-doubtmessages that the server is temporarily storing.
 3. The method of claim2, further comprising waiting, by the server, for client device toindicate whether any of the unique hash codes in the list sent by theserver to the client device are matching unique hash codes that match tothe unique hash codes calculated by the client device for the in-doubtmessages.
 4. The method of claim 3, further comprising receiving, by theserver from the client device, each of the matching unique hash codes inplace of resending the respective one of the in-doubt messagescorresponding thereto to eliminate message resending costs.
 5. Themethod of claim 1, further comprising receiving, by the server from theclient device an explicit indication to include the in-doubt messages aspart of the ongoing unit of work to be committed by the client device.6. The method of claim 1, further comprising: receiving, by the serverfrom the client device, a unique identifier of the client device; andassociating, by the server, the unique identifier with the in-doubtmessages.
 7. The method of claim 1, further comprising retrieving one ormore of the in-doubt messages from the temporary storage location in theserver responsive to the unique hash codes for the one or more of thein-doubt messages matching at both the server and the client device. 8.The method of claim 7, further comprising sending, from the server tothe client device, an acknowledgement that one or more of the in-doubtmessages have been successfully retrieved from the temporary storagelocation in the server, responsive to the one or more of the in-doubtmessages being successfully retrieved from the temporary storagelocation in the server.
 9. The method of claim 8, wherein theacknowledgement indicates that the one or more in-doubt messages areavailable at the server.
 10. The method of claim 1, discarding, by theserver, in the temporary storage location in the server, any of thein-doubt messages for which a respective one of the unique hash codesexists in the list, responsive to receiving, by the server from theclient device, a commit instruction for the transaction that includesthe ongoing unit of work now completed.
 11. The method of claim 1,further comprising discarding the in-doubt messages from the temporarystorage location in the server, responsive to an expiration of apre-determined timeout constraint.
 12. A computer program product forproviding unit of work continuity between a client device and a serverwhen the client device initially fails to complete an ongoing unit ofwork, the computer program product comprising a computer readablestorage medium having program instructions embodied therewith, theprogram instructions executable by a computer to cause the computer toperform a method comprising: temporarily storing, in a temporary storagelocation in the server, in-doubt messages sent to the server for theongoing unit of work, when the client device disconnects from the serverwithout committing the ongoing unit of work and in place of the clientdevice resending the in-doubt messages to the server; receiving, by theserver from the client device, a respective one of unique hash codes,calculated by the client device, for each of the in-doubt messages; andutilizing the unique hash-codes to identify the in-doubt messages theclient device had earlier sent to retrieve the in-doubt messages by theserver from the temporary storage location and include the in-doubtmessages as part of the ongoing unit of work to be committed by theclient device, wherein the ongoing unit of work is only part of anentire transaction.
 13. The computer program product of claim 12,further comprising sending, by the server to the client device, a listof the unique hash-codes for the in-doubt messages that the server istemporarily storing.
 14. The computer program product of claim 13,further comprising waiting, by the server, for client device to indicatewhether any of the unique hash codes in the list sent by the server tothe client device are matching unique hash codes that match to theunique hash codes calculated by the client device for the in-doubtmessages.
 15. The computer program product of claim 14, furthercomprising receiving, by the server from the client device, each of thematching unique hash codes in place of resending the respective one ofthe in-doubt messages corresponding thereto to eliminate messageresending costs.
 16. The computer program product of claim 12, furthercomprising retrieving one or more of the in-doubt messages from thetemporary storage location in the server responsive to the unique hashcodes for the one or more of the in-doubt messages matching at both theserver and the client device.
 17. The computer program product of claim16, further comprising sending, from the server to the client device, anacknowledgement that one or more of the in-doubt messages have beensuccessfully retrieved from the temporary storage location in theserver, responsive to the one or more of the in-doubt messages beingsuccessfully retrieved from the temporary storage location in theserver.
 18. The computer program product of claim 12, discarding, by theserver, in the temporary storage location in the server, any of thein-doubt messages for which a respective one of the unique hash codesexists in the list, responsive to receiving, by the server from theclient device, a commit instruction for the transaction that includesthe ongoing unit of work now completed.
 19. A system, comprising: ahardware server, having a processor, configured to: temporarily store,in a temporary storage location in the server, in-doubt messages sent tothe server for an ongoing unit of work, when a client device disconnectsfrom the server without committing the ongoing unit of work and in placeof the client device resending the in-doubt messages to the server;receive, by the server from the client device, a respective one ofunique hash codes, calculated by the client device, for each of thein-doubt messages; and utilize the unique hash-codes to identify thein-doubt messages the client device had earlier sent to retrieve thein-doubt messages by the server from the temporary storage location andinclude the in-doubt messages as part of the ongoing unit of work to becommitted by the client device, wherein the ongoing unit of work is onlypart of an entire transaction.